Her husband, Tony Award-winning playwright David Rabe, said she died after a 21-year battle with chronic lymphocytic leukemia. She was surrounded by her family when she died at her home in Lakeville, Conn., he said.
In "An Unmarried Woman" (1978), directed by Paul Mazursky, Clayburgh starred opposite Alan Bates and Michael Murphy as a divorcee exploring her sexuality. She was nominated for an Academy Award as best actress but lost to Jane Fonda in "Coming Home." Her second Oscar nomination came for "Starting Over" (1979), Alan J. Pakula's comedy about a divorced man, played by Burt Reynolds, who falls in love but can't get over his ex-wife, played by Candice Bergen. ( Sally Field won for "Norma Rae.")
Her other movie credits include "Semi-Tough," "I'm Dancing As Fast As I Can," "Silver Streak," "First Monday in October" and "Running With Scissors." On Broadway, she appeared in Noel Coward's "Design for Living," the original production of Tom Stoppard's "Jumpers," and the Tony Award-winning musicals "Pippin" and "The Rothschilds."
She appeared on TV shows including "Dirty Sexy Money" and was nominated for two Emmys: for best actress in 1975 for her work on "Hustling" and for her guest turn on "Nip/Tuck" on FX in 2005.
Born April 30, 1944, in New York, Clayburgh came from a privileged family. Her father was vice president of two large companies and her mother was a secretary for Broadway producer David Merrick. Her grandmother, Alma Clayburgh, was an opera singer and New York socialite.
She was entranced seeing Jean Arthur play "Peter Pan" on Broadway, and she and a school friend concocted their own dramatics every day at home. At Sarah Lawrence College, she studied religion, philosophy and literature.
Clayburgh also took drama classes at Sarah Lawrence. She and her friend Robert De Niro acted in a film, "The Wedding Party," directed by a Sarah Lawrence graduate, Brian DePalma. After graduating with a bachelor of arts degree, she began performing in repertory and in Broadway musicals such as "The Rothschilds" and "Pippin."
Alongside Richard Thomas, she headed the 2005 Broadway cast of "A Naked Girl on the Appian Way," Richard Greenberg's comedy about one family's unusual domestic tribulations.
Director Doug Hughes, who directed her in a production of Arthur Miller's "All My Sons" at the Westport Country Playhouse two years ago, called her for "A Naked Girl."
"That she has the time to do a run of a play is just an extraordinary boon because I've had the pleasure of seeing her play a bona fide tragic American role beautifully, and I have had the pleasure of directing her in a very, very smart light comedy and be utterly brilliant in that," he said in 2005.
During an interview that year, Clayburgh explained the unglamorous side of acting.
"One of the funny things about actors is that people look at their careers in retrospect, as if they have a plan," she said.
"Mostly, you just get a call. You're just sitting there going, 'Oh, my God. I'm never going to work again. Oh, God. I'm too old. Maybe I should go and work for Howard Dean.' And then it changes."
Besides her husband, survivors include her daughter, actress Lily Rabe; a son, Michael Rabe; and a stepson, Jason Rabe.
Her family will have a memorial in about six months, though plans have not been finalized.